Bulk silicon mirrors with hinges underneath

ABSTRACT

This invention provides method and apparatus for fabricating a MEMS apparatus having a bulk element with hinges underneath. The bulk element may comprise single-crystal silicon, fabricated by way of bulk micromachining techniques. The hinges may be made of thin-films, fabricated by way of surface micromachining techniques. A distinct feature of the MEMS apparatus of the present invention is that by disposing the hinges underneath the bulk element, the surface of the bulk element can be maximized and the entire surface becomes usable (e.g., for optical beam manipulation). Such a feature would be highly advantageous in making arrayed MEMS devices, such as an array of MEMS mirrors with a high optical fill factor. Further, by advantageously making use of both bulk and surface micromachining techniques, a MEMS mirror thus produced is equipped with a large and flat mirror along with flexible hinges, hence capable of achieving a substantial rotational range at modest electrostatic drive voltages.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of Application No. 10/159,153, filedMay 31, 2002, now U.S. Pat. No. 6,695,457 which claims the benefit ofU.S. Provisional Patent Application No. 60/295,682. filed on 2 Jun.2001.

FIELD OF THE INVENTION

This invention relates generally to micro-electro-mechanical systems(MEMS). In particular, it provides method and system for making MEMSmirrors by a combination of bulk and surface micromachining techniques.

BACKGROUND OF THE INVENTION

MEMS mirrors have demonstrated to be effective in a variety ofapplications, including high-speed scanning and optical switching. Insuch applications, it is essential for MEMS mirrors to have flat opticalsurfaces, large rotational range, and robust performance.

Many applications (e.g., optical networking applications) furtherrequire that MEMS mirrors be configured in a closely packed array. It istherefore desirable to maximize the “optical fill factor” of the array(i.e., by making the optical surface of each constituent mirror as largeas possible), without compromising other essential characteristics.

MEMS mirrors are conventionally made by either bulk or surface siliconmicromachining techniques. Bulk micromachining, which typically producessingle-crystal silicon mirrors, is known to have a number of advantagesover surface micromachining, which typically produces polysilicon (orthin-film) mirrors. For example, single-crystal silicon mirrors producedby bulk micromachining techniques are generally thicker and largermirrors with smoother surfaces and less intrinsic stress thanpolysilicon (or thin-film) mirrors. Low intrinsic stress and sizeablethickness result in flat mirrors, while smooth surfaces reduce lightscattering. An advantage inherent to surface micromachining techniquesis that the mirror suspension (e.g., one or more thin-film hinges) canbe better defined and therefore made smaller. This allows the MEMSmirror thus produced to have a large rotational range, e.g., at moderatedrive voltages.

U.S. Pat. No. 6,028,689 of Michalicek et al. (“Michalicek et al.”)discloses a movable micromirror assembly, driven by an electrostaticmechanism. The assembly includes a mirror supported by a plurality offlexure arms situated under the mirror. The flexure arms are in turnmounted on a support post. Because the assembly disclosed by Michaliceket al. is fabricated entirely by way of surface micromachiningtechniques, the resulting “micromirror” is of the polysilicon(thin-film) type and is thus subject to the aforementioneddisadvantages.

International Patent Application Number WO 01/94253 A2 of Chong et al.discloses a MEMS mirror device having a bulk silicon mirror attached toa frame by thin-film hinges. A notable shortcoming of this system isevident in that the thin-film hinges extend from the reflective surfaceside of the mirror to the frame, hence restricting (or obstructing) theamount of surface area available for optical beam manipulation. Thisshortcoming further results in a lower optical fill factor in an arrayof such MEMS devices.

Tuantranont et al. disclose an array of deflectable mirrors fabricatedby a surface micromachining polysilicon (or “MUMPS”) process in“Bulk-Etched Micromachined and Flip-Chip Integrated Micromirror Arrayfor Infrared Applications,” 2000 IEEE/LEOS International Conference onOptical MEMS, 21024, Kauai, Hi. (August 2000). In this case, an array ofpolysilicon mirror plates is bonded to another array of thermal bimorphactuators by gold posts using the “flip-chip transfer technique”,resulting in trampoline-type polysilicon plates each suspended at itscorners by thermal bimorph actuators. In addition to the mirror platesmade of polysilicon (or thin-film), another drawback of thethus-constructed mirror array is the lack of a monolithic structure,which makes the array susceptible to misalignment and other extraneousundesirable effects.

In view of the foregoing, there is a need in the art to provide a noveltype of MEMS mirrors that overcomes the limitations of prior devices ina simple and robust construction.

SUMMARY OF THE INVENTION

The present invention provides a MEMS apparatus, including a bulkelement; a support; and one or more hinges. The bulk element comprises adevice surface and a bottom surface that is situated below the devicesurface. The hinges are disposed below the bottom surface of the bulkelement and couple the bulk element to the support, whereby the bulkelement is suspended from the support.

In the above apparatus, the support may include a cavity, in which thehinges are disposed. There may be at least one electrode disposed in thecavity, for causing the bulk element to be actuated. The device surfaceof the bulk element may further contain a reflective layer (e.g., ametallic film), rendering the apparatus thus constructed a MEMS mirror.

In the present invention, the term “bulk element” refers to an elementfabricated by bulk micromachining techniques known in the art, whichtypically comprises a single-crystal material. A case in point may be asingle-crystal silicon element. The bulk element is characterized by a“device” surface and a “bottom” surface that is situated below thedevice surface (while the bulk element itself may assume any geometricform deemed suitable). The “device” surface of the bulk element may beoptically reflective. It may also be used as an “interface” for couplingthe bulk element to other devices, if so desired in a practicalapplication. Further, a “support” may be a frame or substrate, to whichthe bulk element is attached. A “hinge” (or “hinge element”) should beconstrued broadly as any suspension/coupling means that enables the bulkelement to be suspended from the support and further provides therestoring force as the bulk element undergoes motion. For instance, ahinge may be a flexure or flexible coupling, e.g., fabricated by a bulkor surface micromachining technique known in the art. The term“underneath” refers to the hinges being anchored to (or below) thebottom surface of the bulk element and thereby disposed wholly beneaththe device surface. This allows the device surface of the bulk elementto be maximized and the entire surface to be usable (e.g., for opticalreflection).

The present invention further provides a process flow (or method) thatmay be used for fabricating the aforementioned MEMS apparatus. In oneembodiment of a process flow according to the present invention, a“device” component is formed. The device component in one form may beprovided by an SOI (Silicon-On-Insulation) wafer, comprising asingle-crystal silicon device layer and a silicon handle wafer with aninsulation layer (e.g., silicon oxide) sandwiched in between. First andsecond hinge elements may be fabricated on a first surface of thesingle-crystal silicon layer, e.g., by way of surface micromachiningtechniques. A “support” component is configured to contain a cavity, inwhich at least one electrode may be disposed. Subsequently, the deviceand support components are bonded in such a manner that the hingeelements are disposed within the cavity. The silicon handle wafer alongwith the insulation layer in the device component is then removed,thereby revealing a second surface of the single-crystal silicon devicelayer. A bulk element may be subsequently produced in the single-crystalsilicon device layer by way of bulk micromachining techniques,characterized by the first and second surfaces. The configuration may besuch that the hinge elements are each anchored to the first (or“bottom”) surface of the bulk element on one end and to the supportcomponent on the other, thereby enabling the bulk element to besuspended with the hinge elements wholly underneath the second (or“device”) surface. A reflective layer may be further deposited on thedevice surface of the bulk element, rendering the apparatus thusconstructed a MEMS mirror.

One advantage of the MEMS apparatus of the present invention is that byplacing the hinge elements underneath the bulk element, the devicesurface of the bulk element can be maximized and the entire surfacebecomes usable (e.g., for optical beam manipulation). Such a featurewould be highly advantageous in making arrayed MEMS devices, such as anarray of MEMS mirrors with a high optical fill factor. Further, byadvantageously making use of both bulk and surface micromachiningtechniques, a MEMS mirror of the present invention is equipped with alarge and flat mirror along with flexible hinges, and is hence capableof achieving a substantial rotational range at moderate electrostaticdrive voltages. An additional advantage of the MEMS apparatus of thepresent invention is evident in its monolithic structure, rendering itrobust in performance. These advantageous features are in notablecontrast with the prior devices described above.

The novel features of this invention, as well as the invention itself,will be best understood from the following drawings and detaileddescription.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A is a schematic side sectional view of a first embodiment of aMEMS apparatus, according to the present invention;

FIG. 1B is a schematic top view of a first embodiment of a MEMSapparatus, according to the present invention;

FIG. 2 is a schematic side sectional view of a second embodiment of aMEMS apparatus, according to the present invention;

FIG. 3 is a schematic side sectional view of a third embodiment of aMEMS apparatus, according to the present invention; and

FIGS. 4A-4F show an exemplary process flow for fabricating a MEMSapparatus, according to the present invention.

DETAILED DESCRIPTION

FIGS. 1A-1B illustrate a first embodiment of a MEMS apparatus, accordingto the present invention. FIG. 1A depicts a schematic side sectionalview of a MEMS apparatus 100, comprising a bulk element 110; first andsecond hinge elements 121, 122; and a support 130. The bulk element 110may have a “device” (or “top”) surface 112, and a “bottom” surface 111which is disposed below and opposes the device surface 112. The firstand second hinge elements 121, 122 are each disposed below the devicesurface 112. As a way of example in the embodiment of FIG. 1A, the hingeelements 121, 122 are each coupled to the bottom surface 111 of the bulkelement 110 on one end and to the support 130 on the other. In thismanner, the bulk element 110 is suspended with the hinge elements 121,122 disposed wholly underneath the device surface 112.

FIG. 1B shows a schematic top view of the MEMS apparatus 100. By way ofexample, the device surface 112 of the bulk element 110 is shown to begenerally rectangular in shape. It will be appreciated that this neednot be case; in fact, the device surface of a bulk element (or the bulkelement itself) in the present invention may assume any geometric form(e.g., elliptical) that is deemed suitable for a given application.

In the embodiment of FIGS. 1A-1B, the support 130 may include asubstrate portion 131 and a cavity 140. By way of example, the substrateportion 131 may be generally rectangular in shape. A plurality ofsidewalls 132, 133, 134, 135 may extend from the portion 131 and therebyform the cavity 140. As shown in FIG. 1A, the hinge elements 121, 122are disposed within the cavity 140, and are coupled respectively to thesidewalls 133, 135. In the embodiment of FIGS. 1A-1B, each of thesidewalls 132, 133, 134, 135 may include a corresponding ridge (or“lip”) portion 142, 143, 144, 145 that projects inward from therespective sidewall (see the ridge portions 143, 145 shown in FIG. 1A,for example). Furthermore, the hinge elements 121, 122 have a generally“C”-shaped (side-view) cross-section, and are coupled to the ridgeportions 143, 145 of the sidewalls 133, 135, respectively. However, thisshould not be viewed as limiting in any way. For example, in alternateembodiments, the hinge elements 121, 122 may assume any other suitableshape or cross-section. They may also be coupled to other portions ofthe sidewalls 133, 135.

In the embodiment shown in FIGS. 1A-1B, the cavity 140 is shown to begenerally rectangular in shape. However, in alternate embodiments, thecavity 140 may assume any other suitable geometric form. The cavity 140may include at least one electrode 141, which may be disposed on abottom surface 150 of the cavity 140. The electrode 141 is adapted tocause the bulk element 110 to be actuated in a known manner (e.g., in anelectro-static fashion). Moreover, the device surface 112 of the bulkelement 110 may be optically reflective, e.g., by way of polishingand/or depositing a metallic film on the surface.

FIG. 2 shows a schematic side sectional view of a second embodiment of aMEMS apparatus. By way of example, MEMS apparatus 200 may comprise abulk element 210; first and second hinge elements 221, 222; and asupport 230. The bulk element 210 may include a “device” (or “top”)surface 212, and a “bottom” surface 211 which is disposed below andopposes the device surface 212. In this embodiment, the bulk element 210may further include a base portion 215, which may extend downward fromthe bottom surface 211. The first and second hinge elements 221, 222 areeach disposed below the device surface 212. As a way of example, thefirst and second hinge elements 221, 222 are each shown to be coupled tothe base portion 215 of the bulk element 110 on one end and to thesupport 130 on the other. In this manner, the bulk element 210 issuspended with the hinge elements 221, 222 disposed wholly underneaththe device surface 212.

In the embodiment of FIG. 2, the support 230 may include a substrateportion 231 and a cavity 240. By way of example, the substrate portion231 may be generally rectangular in shape. A plurality of sidewalls 233,235 extend from the portion 231 and thereby form the cavity 240. Thehinge elements 221, 222 are disposed within the cavity 240. In thepresent embodiment, the hinge elements 221, 222 may extend in agenerally horizontal direction, thereby coupling the base portion 215 tothe sidewalls 233, 235, respectively. However, this should not be viewedas limiting in any way. For example, in alternate embodiments, the hingeelements 221, 222 may assume any other suitable shape. They may also bepositioned in other directions, and/or coupled to other portions of thesidewalls 233, 235.

The cavity 240 may be of any suitable shape in the embodiment of FIG. 2.The cavity 240 may include at least one electrode 241, which may bedisposed on a bottom surface 250 of the cavity 240. The electrode 241 isadapted to cause the bulk element 210 to be actuated in a known manner(e.g., electro-statically). The device surface 212 of the bulk element210 may likewise be optically reflective, e.g., by way of polishingand/or depositing a metallic film on the surface.

FIG. 3 shows a schematic side sectional view of a third embodiment of aMEMS apparatus 300. With the exception of a bulk element 310, MEMSapparatus 300 is shown to be substantially similar to the MEMS apparatus200, and may make use of the general configuration of and a number ofthe elements shown in FIG. 2. As shown in FIG. 3, the MEMS apparatus 300may comprise a bulk element 310; first and second hinge elements 321,322; and a support 330. The support 330 may include a cavity 340, whichis formed by at least two sidewalls 333, 335 that extend from substrateportion 331. The cavity 340 may include a bottom surface 350, on whichat least one electrode 341 may be disposed.

In the MEMS apparatus 300, the bulk element 310 may include a “device”(or “top”) surface 312, and a “bottom” surface 311 which is disposedbelow and opposes the device surface 312. As a way of example, the bulkelement 310 is shown to include a generally “T”-shaped base portion 315.The base portion 315 extends downward from the bottom surface 311 andforms side cavities or “voids” 316, 317 in the bulk element 310. As inthe embodiment of FIG. 2, the first and second hinge elements 321, 322are each disposed beneath the bottom surface 311 of the bulk element310. In the present embodiment, the hinge elements 321, 322 are eachshown to be coupled to the base portion 315 of the bulk element 310within the respective voids 316, 317 on one end and to the respectivesidewalls 333, 335 of the support 330 on the other. In this manner, thebulk element 310 is suspended with the hinge elements 321, 322 disposedwholly underneath the device surface 312.

In the foregoing embodiments and in an exemplary fabrication processdescribed below, the term “bulk element” (e.g., the bulk element 110,210, or 310) refers to an element fabricated by bulk micromachiningtechniques known in the art, which typically comprises a single-crystalmaterial. For example, the bulk elements 110, 210, 310 shown above mayeach be a single-crystal silicon element. The bulk element ischaracterized by a “device” surface and a “bottom” surface that issituated below the device surface; while the bulk element itself mayassume any geometric form that is appropriate for a given application.(It will be appreciated that the device and bottom surfaces need not beopposing one another, in general.) The “device” surface of a bulkelement may be optically reflective. An optical element (e.g., agrating) may also be patterned on it. Additionally, the device surfacemay be used as an “interface” for coupling the bulk element to otherdevices, if so desired in practical applications.

Further, a “support” (e.g., the support 130, 230, or 330) may be a frameor substrate, to which the bulk element is attached. A “hinge” (or“hinge element”) should be construed broadly as any suspension/couplingmeans that enables the bulk element to be suspended from the support andfurther provides the restoring force as the bulk element undergoesmotion (e.g., due to the actuation mechanism caused by the electrode 141of FIGS. 1A-1B). As a way of example, the first or second hinge elementshown in FIG. 1A, 2, or 3 may be a flexure or flexible coupling, e.g.,fabricated by bulk or surface micromachining techniques known in theart. While two hinge elements are shown in each of the foregoingembodiments, alternate embodiments may include a fewer or greater numberof hinge elements. The term “underneath” refers to a hinge element beinganchored to (or below) the bottom surface of the bulk element andthereby disposed wholly beneath the device surface. This allows thedevice surface of the bulk element to be maximized and the entiresurface to be usable (e.g., for optical beam manipulation), as the aboveembodiments illustrate.

FIGS. 4A-4F show an exemplary embodiment of a process flow, which may beutilized for fabricating a MEMS apparatus (e.g., the embodiment of FIGS.1A-1B) according to the present invention. FIG. 4A shows a schematicside sectional view of a “device” component 400, which in one form maybe an SOI (Silicon On Insulator) wafer, comprising a single-crystalsilicon “device” layer 415 and a silicon “handle wafer” 417 with a firstinsulation layer 416 (e.g., silicon oxide) sandwiched therein between.The single-crystal silicon device layer 415 may have a predeterminedthickness d, which may be on the order of 5-100 μm. First and secondhinge elements 421, 422 are fabricated on a first surface 411 of thesingle-crystal silicon device layer 415 in a known manner, e.g., by aknown surface micromachining technique. Each hinge element may be athin-film, e.g., composed of polysilicon, polyoxide, nitride, siliconnitride, silicon oxide, silicon oxynitride, or a metal. First and second“sacrificial” elements 423, 424 (which may be formed from silicon oxide)may be first patterned on the first surface 411, prior to forming thefirst and second hinge elements 421, 422, respectively.

FIG. 4B shows a schematic side sectional view of a “support” component450 containing an “open-ended” cavity 440. As a way of example, thecavity 440 may be formed by a substrate wafer 431 and a plurality ofspacers 433, 435 which form sidewalls of the cavity 440. There may be atleast one electrode 441 disposed in the cavity 440, e.g., patterned onthe substrate wafer 431 via a second insulation layer 432 which may bemade of silicon oxide.

Referring now to FIG. 4C. The device component 400 formed in FIG. 4A isbonded with the support component 450 of FIG. 4B in such a manner thatthe first and second hinge elements 421, 422 are disposed (oraccommodated) within the cavity 440. In the next step of the fabricationprocess flow, illustrated in FIG. 4D, the silicon handle wafer 417(along with the first insulation layer 416) is removed, therebyrevealing a second surface 412 of the single-crystal silicon devicelayer 415.

In the subsequent step of the fabrication process flow, depicted in FIG.4E, a “bulk element” 410 is formed in the single-crystal silicon devicelayer 415 by a known bulk micromachining technique (e.g., a DRIE (DeepReactive Ion Etching) process) known in the art. The formed bulk element410 is also characterized by the first and second surfaces 411, 412 thatoppose one another. In the next step of the fabrication process flow,shown in FIG. 4F, the bulk element 410 is “released”, e.g., by removingthe first and second sacrificial elements 423, 424. Note that theremainder of the single-crystal silicon device layer 415, the spacers433, 435, and the support wafer 431 form an integrated support structure430, which may substantially constitute the support 130 in theembodiment of FIGS. 1A-1B, for instance. (Those skilled in the art willappreciate that first and second sacrificial elements 423, 424 may alsobe removed earlier, e.g., anywhere in the fabrication process flow afterthe step of FIG. 4A.)

A reflective layer 402 (e.g., a gold film) may be further deposited onthe second surface 412 of the bulk element 410, rendering the apparatusthus constructed a MEMS mirror. Note that because the first and secondhinge elements 421, 422 are anchored to the first (or “bottom”) surface411 and thereby wholly “underneath” the bulk element 410 thus produced,the second (or “device”) surface 412 of the bulk element 410 can bemaximized and the entire surface becomes usable (e.g., for opticalreflection). Furthermore, being situated in a cavity (e.g., the cavity440), the first and second hinge elements 421, 422 can be madesufficiently long/large, if so desired in a given application.

In the aforementioned process flow, use of an SOI wafer for the devicecomponent 400 of FIG. 4A has the advantages of providing precise controlof the thickness of the bulk element 410 (by way of the predeterminedthickness d of the single-crystal silicon device layer of the SOI wafer)and ease in manipulation (owing to the handle wafer of the SOI wafer),while the intervening insulation layer of the SOI wafer may serve as aconvenient “etch-stop” (e.g., when removing the handle wafer). The hingeelements may also be fabricated by a known bulk micromachining technique(e.g., the SCREAM (Single Crystal Reactive Etching and Metallization)process known in the art). It will be appreciated, however, that adevice component in the present invention may alternatively be formed inan epitaxial silicon wafer, or a single piece of single-crystal silicon,where the hinge elements may be fabricated in a manner similar to thatdescribed above.

The support component 450 of FIG. 4B may likewise be fabricated out ofan SOI wafer which may be similar to that shown in FIG. 4A inconfiguration. As a way of example, the silicon device layer (e.g.,50-100 μm in thickness) of the SOI wafer may be used to form the spacers433, 435 along with the electrode 441 (e.g., by way of etching), whilethe corresponding handle wafer may serve as the substrate wafer 431.Alternatively, a glass wafer may be used to form the substrate wafer431, on which the electrode 441 may be deposited (e.g., by a knownsurface micromachining technique) and the spacers 433, 435 (e.g., madeof silicon) bonded. The support component 450 of FIG. 4B may also befabricated out of a single piece of a desired material (e.g., a siliconor glass wafer) using an appropriate technique known in the art. Thoseskilled in the art will appreciate that a support component in thepresent invention may generally be configured in any way that issuitable for a given application; what is important is that the supportelement thus configured contains an open-ended cavity (so as to host thehinge elements), e.g., in a manner as illustrated with respect to FIG.4B.

A distinct feature of the fabrication process flow of FIGS. 4A-4F isthat the device component 400 and the support component 450 are bondedin such a manner that the hinge elements are disposed within (oraccommodated by) the cavity 440 of the support component 450 (e.g., seeFIG. 4C above), thereby allowing the hinge elements to be situated“underneath” the bulk element thus produced. One skilled in the art willknow how to apply a suitable process known in the art that is effectivefor carrying out the requisite bonding (e.g., fusion or anodic bonding).It will be appreciated that various elements in the embodiment of FIGS.4A-4F are shown as a way of example to illustrate the general principlesof the present invention, and therefore are not drawn to scale (e.g., ineither geometric shape or size). From the teaching of the presentinvention, those skilled in the art will know how to implement thefabrication process flow of FIGS. 4A-4F in a given application, toproduce a suitable MEMS apparatus according to the present invention.

An advantage of the MEMS apparatus of the present invention is that byplacing the hinge elements underneath the bulk element, the devicesurface of the bulk element can be maximized and the entire surfacebecomes usable (e.g., for optical beam manipulation). Such a featurewould be highly advantageous in making arrayed MEMS devices, such as anarray of MEMS mirrors with a high optical fill factor. Further, byadvantageously making use of a combination of bulk and surfacemicromachining techniques, a MEMS mirror according to the presentinvention may be equipped with a large and flat mirror along withflexible hinges, thereby capable of providing a substantial rotationalrange at moderate electrostatic drive voltages. An additional advantageof the MEMS apparatus of the present invention is evident in itsmonolithic structure, rendering it robust in performance. Theseadvantageous features are in notable contrast with the prior devicesdescribed above. As such, the present invention may be used in a varietyof applications, e.g., providing arrayed MEMS mirrors (or beam steeringdevices) for optical networking applications.

Those skilled in the art will recognize that the exemplary embodimentsdescribed above are provided by way of example to illustrate the generalprinciples of the present invention. Various means and methods can bedevised herein to perform the designated functions in an equivalentmanner. Moreover, various changes, substitutions, and alternations canbe made herein without departing from the principles and the scope ofthe invention. Accordingly, the scope of the present invention should bedetermined by the following claims and their legal equivalents.

What is claimed is:
 1. A method of making a MEMS apparatus, comprising:a) providing a device component comprising single-crystal silicon; b)creating at least one hinge in said device component; c) constructing asupport component having a cavity; d) bonding said device component tosaid support component, such that said at least one hinge is disposedwithin said cavity; and e) forming in said device component a bulkelement having a device surface and a bottom surface, whereby said atleast one hinge is coupled to said bulk element and is disposed belowsaid bottom surface, thereby suspending said bulk element from saidsupport.
 2. The method of claim 1 wherein said device componentcomprises an SOI (Silicon-On-Insulator) wafer having a single-crystalsilicon device layer and a silicon handle wafer sandwiching aninsulation layer, said single-crystal silicon layer having a firstsurface.
 3. The method of claim 2 wherein said at least one hingecomprises first and second hinge elements, fabricated on said firstsurface of said single-crystal silicon device layer by a surfacemicromachining technique.
 4. The method of claim 2 wherein said at leastone hinge is created in said single-crystal silicon device layer by abulk micromachining technique.
 5. The method of claim 3 wherein saidstep d) further includes removing said silicon handle wafer along withsaid insulation layer, thereby revealing a second surface of saidsingle-crystal silicon device layer.
 6. The method of claim 5 whereinsaid step e) includes using a bulk micromachining technique to form saidbulk element in said single-crystal silicon device layer, whereby saidfirst and second surfaces of said single-crystal silicon device layerconstitute said bottom and device surfaces of said bulk element.
 7. Themethod of claim 1 further comprising the step of making said devicesurface optically reflective.
 8. The method of claim 7 wherein saiddevice surface is made optically reflective by depositing a reflectivelayer thereon.
 9. The method of claim 1 wherein said device componentcomprises. an epitaxial silicon wafer.
 10. The method of claim 1 whereinsaid support component is fabricated out of an SOI wafer.
 11. The methodof claim 1 wherein said step c) further includes disposing at least oneelectrode in said cavity.